所以我有一个包含两个表的数据库，一个用于名为 tblactivity 另一个叫 tblusers : tblactivity 包含一个用户的多个数据，我想在 tblactivity 在基于我从其获取数据的登录用户的recyclerview中 tblusers . tblactivity 有 userid 我想知道该怎么办。
编辑：更多详细信息：
所以我使用slim框架：dbconnect.php

//Method to get emails of a particular user

    public function getActivity(){
        $stmt = $this->con->prepare("SELECT id, userid, subject, message FROM tblactivity");
        $stmt->execute(); 
        $stmt->bind_result($id, $userid, $subject, $message);
        $users = array(); 
        while($stmt->fetch()){ 
            $user = array(); 
            $user['id'] = $id; 
            $user['userid'] = $userid; 
            $user['subject'] = $subject; 
            $user['message'] = $message; 

            array_push($users, $user);
        }             
        return $users; 

    }

my index.php代码

$app->get('/allactivity', function(Request $request, Response $response){
$db = new DbOperations; 
$users = $db->getActivity();
$response_data = array();
$response_data['error'] = false; 
$response_data['users'] = $users; 
$response->write(json_encode($response_data));
return $response
->withHeader('Content-type', 'application/json')
->withStatus(200);  
});

现在在android studio中：
my activity.java模型：

public class Activity {

private int id;
private int userid;
private String subject;
private String message;
private String to;

public Activity(String subject, String message) {

    this.id = id;
    this.userid = userid;
    this.subject = subject;
    this.message = message;
    this.to = to;

}

public int getId() {
    return id;
}
public int getUserid() { return userid; }
public String getSubject() { return subject; }
public String getMessage() {
    return message;
}
public String getTo() { return to; }

}

user.java模型

public class User {
private int id;
private String email;
private String firstname;
private String lastname;
private String companyname;
private String postcode;
private String city;
private String state;
private String phonenumber;
private String address1;
private String country;
private String status;
private int currency;
private String credit;
private String language;
private int email_verified;

public User(int id, String email, String firstname, String lastname, String companyname, String address1, String city,
            String state, String postcode, String country, String phonenumber, String status, int currency, String credit,
            String language, int email_verified) {

    this.id = id;
    this.email = email;
    this.firstname = firstname;
    this.lastname = lastname;
    this.companyname = companyname;
    this.address1 = address1;
    this.city = city;
    this.state = state;
    this.postcode = postcode;
    this.country = country;
    this.phonenumber = phonenumber;
    this.status = status;
    this.currency = currency;
    this.credit = credit;
    this.language = language;
    this.email_verified = email_verified;

}

public int getId() {
    return id;
}
public String getEmail() {
    return email;
}
public String getFirstName() {
    return firstname;
}
public String getLastName() {
    return lastname;
}
public String getCompanyName() { return companyname; }
public String getAddress1() {
    return address1;
}
public String getCity() {
    return city;
}
public String getState() { return state; }
public String getPostcode() {
    return postcode;
}
public String getCountry() {
    return country;
}
public String getPhonenumber() {
    return phonenumber;
}
public String getStatus() { return status; }
public int getCurrency() { return currency; }
public String getCredit() {
    return credit;
}
public String getLanguage() {
    return language;
}
public int getEmail_verified() { return email_verified; }

}

我使用改造客户机从php获取json输出。

@GET("allactivity")
Call<List<Activity>> getActivityData();

}